1. Field of the Invention
The present invention relates to video display apparatuses that display color video, and more particularly to video display apparatuses that have a function of adjusting the color balance.
2. Description of Related Art
A video display apparatus displays video on a display panel such as a liquid crystal panel based on a video signal (input signal) from an external device or from a broadcast wave. When the input signal is displayed unprocessed, the video display apparatus may, depending on the characteristics of the display panel, display video with varying display characteristics.
To cope with that, most video display apparatuses are, for the purpose of obtaining displayed video with desired display quality, provided with a corrector (circuit) for correcting the luminance of input data (gamma correction) and for adjusting the chromaticity thereof (white balance adjustment). As one such correction method, a correction method is used according to which an LUT (look-up table) is applied to an input signal to convert its gradation values to obtain a desired output (see, for example, Patent Document 1). By correcting the input signal in such a way, it is possible to display video with standard display quality, and to form video with luminance that suits the user's preference.
According to Japan Patent Publication No. 4829905 (Patent Document 1), the user arbitrarily sets a maximum input value and a minimum input value along with a control value. Based on these values, conversion data for obtaining a curve (gamma curve) for gamma correction is recorded in an LUT, and by use of this LUT, gamma correction is performed. By a gamma correction method like this, it is possible to adjust luminance levels properly over a wide range of input gradations.
However, in gamma correction according to Patent Document 1, to determine conversion data, it is necessary to set three points, namely a maximum point which takes the maximum input gradation value within the adjustment range, a minimum point which takes the minimum input gradation value there, and an arbitrary adjustment point between the maximum and minimum points. Thus, gamma correction takes time and trouble. This method of determining set values of conversion data for gamma correction can be used in white balance adjustment. However, it is then necessary to determine conversion data for each of R, G, and B data of an input signal. This takes more time and more trouble, which is inconvenient to the user.